Selective determination of o-phenylenediamine by surface-enhanced Raman spectroscopy using silver nanoparticles decorated with α-cyclodextrin

We have developed a SERS method for the determination of o-phenylenediamine (OPD) in water. It is based on the chemical cyclization reaction of OPD with nitrite in acidic medium. Benzotriazole (BTAH), one of the products of the reaction, can be determined by SERS with high sensitivity when using silver nanoparticles decorated with alpha-cyclodextrin (alpha-CD-AgNPs) as a substrate. The acidity of the medium, nitrite concentration, reaction time and mixing time for solutions of analytes and SERS substrates were optimized. The enhancement factors of the optimal SERS substrates (even if stored for a few months) range from 2.17 x 10(6) to 2.52 x 10(6) when utilizing the SERS peak at 1,602 cm(-1). Other figures of merit include (a) a linear analytical range from 0.10 to 1.0 mu mol L-1, (b) a detection limit of 30 nmol L-1, and (c) a quantification limit at 100 nmol L-1. The high selectivity for OPD was confirmed by studies on the potentially interfering species m- and p-phenylenediamine, aniline, and 1-naphthylamine. Recoveries of OPD from spiked real water samples ranged from 97.8 to 104.5 %, with relative standard deviations of less than 4 %.